ILLUSTRATING CARRIAGE OF MOMENTUM 6l 



indicated by the arrow. One set of readings, made 

 under good conditions, gave a mean deflexion of 

 3*3 scale divisions, corresponding to a torque of 

 20 x icr 6 cm. dynes. The energy of the beam was 

 measured, and after allowing for reflexions, it 

 should have produced a torque of 20*3 X io~ 6 cm. 

 dynes. Other observations of the torque were not 

 so near that calculated from the energy, though 

 always of the right order. 



FIG. 27. 



Another smaller pair of prisms was then used, 

 with the same refracting angle of 34, but with 

 sloping side only 1*35 cm. long and I '05 cm. high. 

 It was hoped that with this lighter system and a 

 smaller and presumably more uniform beam, the 

 results would be more consistent, but the hope was 

 not justified, as the following observations in four 

 experiments show. The torque was too small for 

 accurate measurement. 



